With ongoing improvements in the digitization of information, data embedding methods as represented by the electronic watermark method have come into common use, and have come to be applied to the analog image medium such as printed matters and reproductions in recent years.
The data embedding method for printed matters is represented by the technique wherein, for example, dots are arranged at equally spaced intervals as a background of the document image and others at the time of printing, and whereby data is embedded as the dot arrangement and profile.
To detect the embedded data, when the document image is read by a scanner etc., the dot arrangement and profile reproduced together with the document image are detected, and the embedded data is extracted and restored.
One of the techniques related to embedding and detection of data using dots is the method of generating a background wherein a reproduction prohibition pattern image area and the conditional pattern image area for canceling the reproduction prohibition are repeatedly arranged in a two-dimensional array according to a predetermined rule, and are overlapped with the document image, whereby a composite image is generated (for example, Patent Literature 1).
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2003-283790